Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B37/00—Lapping machines or devices; Accessories
  • B24B37/11—Lapping tools
  • B24B37/20—Lapping pads for working plane surfaces
  • B24B37/24—Lapping pads for working plane surfaces characterised by the composition or properties of the pad materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/48—Polyethers
  • C08G18/4854—Polyethers containing oxyalkylene groups having four carbon atoms in the alkylene group

Definitions

• Polyurethane polishing pads are the primary pad-type for a variety of demanding precision polishing applications. These polyurethane polishing pads are effective for polishing silicon wafers, patterned wafers, flat panel displays and magnetic storage disks.
• polyurethane polishing pads provide the mechanical integrity and chemical resistance for most polishing operations used to fabricate integrated circuits. For example, polyurethane polishing pads have high strength for resisting tearing; abrasion resistance for avoiding wear problems during polishing; and stability for resisting attack by strong acidic and strong caustic polishing solutions.
• CMP chemical mechanical planarization
• the invention provides a polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates, the polishing pad comprising a cast polyurethane polymeric material formed from a prepolymer reaction of a prepolymer polyol and a polyfunctional aromatic isocyanate to form an isocyanate-terminated reaction product, the polyfunctional aromatic isocyanate having less than 8 weight percent aliphatic isocyanate and the isocyanate-terminated reaction product having 4.5 to 8.7 weight percent unreacted NCO, the isocyanate-terminated reaction product being cured with a curative agent selected from the group comprising curative polyamines, curative polyols, curative alcoholamines and mixtures thereof; and the polishing pad containing at least 0.1 volume percent filler or porosity.
• the invention provides a polishing pad suitable for planarizing semiconductor substrates, the polishing pad comprising a cast polyurethane polymeric material formed from a prepolymer reaction of a prepolymer polyol selected from the group comprising polytetramethylene ether glycol, polyester polyols, polypropylene ether glycols, copolymers thereof and mixtures thereof and a polyfunctional aromatic isocyanate to form an isocyanate-terminated reaction product, the polyfunctional aromatic isocyanate having less than 5 weight percent aliphatic isocyanate and the isocyanate-terminated reaction product having 4.5 to 8.7 weight percent unreacted NCO, the isocyanate-terminated reaction product being cured with a curative agent with expandable polymeric microspheres, the curative agent selected from the group comprising curative polyamines, curative polyols, curative alcoholamines and mixtures thereof; and the polishing pad containing a porosity of at least 0.1 volume percent.
• the invention provides a method of forming a polishing pad suitable for planarizing semiconductor substrates comprising casting polyurethane polymeric material from a prepolymer reaction of a prepolymer polyol and a polyfunctional aromatic isocyanate to form an isocyanate-terminated reaction product, the polyfunctional aromatic isocyanate having less than 8 weight percent aliphatic isocyanate and the isocyanate-terminated reaction product having 4.5 to 8.7 weight percent unreacted NCO, the isocyanate-terminated reaction product being cured with a curative agent selected from the group comprising curative polyamines, curative polyols, curative alcoholamines and mixtures thereof; and the polishing pad containing at least 0.1 volume percent filler or porosity.
• Cast polyurethane polishing pads are suitable for planarizing semiconductor, optical and magnetic substrates.
• the pads' particular polishing properties arise in part from a prepolymer reaction product of a prepolymer polyol and a polyfunctional isocyanate.
• the prepolymer product is cured with a curative agent selected from the group comprising curative polyamines, curative polyols, curative alcohol amines and mixtures thereof to form a polishing pad. It has been discovered that controlling the amount of unreacted NCO in the prepolymer reaction product can improve porous pads' uniformity throughout a polyurethane casting.
• the polyurethane will have too long of a gel time that can also lead to non-uniformity, such as, the sinking of high-density particles or floating of low-density particles and pores during an extended gelation process.
• Controlling the prepolymer' s weight percent unreated NCO to between 4.5 and 8.7 weight percent provides cast polyurethane polishing pads with uniform properties.
• the prepolymer's weight percent unreacted NCO is between 4.7 and 8.5.
• the polymer is effective for forming porous and filled polishing pads.
• filler for polishing pads include solid particles that dislodge or dissolve during polishing, and liquid-filled particles or spheres.
• porosity includes gas-filled particles, gas-filled spheres and voids formed from other means, such as mechanically frothing gas into a viscous system, injecting gas into the polyurethane melt, introducing gas in situ using a chemical reaction with gaseous product,or decreasing pressure to cause disolved gas to form bubbles.
• the polishing pads contain a porosity or filler concentration of at least 0.1 volume percent. This porosity or filler contributes to the polishing pad's ability to transfer polishing fluids during polishing.
• the polishing pad has a porosity or filler concentration of 0.2 to 70 volume percent.
• the polishing pad has a porosity or filler concentration of 0.25 to 60 volume percent.
• the pores or filler particles have a weight average diameter of 10 to 100 ⁇ m. Most preferably, the pores or filler particles have a weight average diameter of 15 to 90 ⁇ m. The nominal range of expanded hollow-polymeric microspheres' weight average diameters is 15 to 50 ⁇ m. Controlling the unreacted NCO concentration is particularly effective for controlling the pore uniformity for pores formed directly or indirectly with a filler gas. This is because gases tend to undergo thermal expansion at a much greater rate and to a greater extent than solids and liquids.
• the method is particularly effective for porosity formed by casting hollow microspheres, either pre-expanded or expanded in situ; by using chemical foaming agents; by mechanically frothing in gas; and by use of dissolved gases, such as argon, carbon dioxide, helium, nitrogen, and air, or supercritical fluids, such as supercritical carbon dioxide or gases formed in situ as a reaction product.
• gases such as argon, carbon dioxide, helium, nitrogen, and air
• supercritical fluids such as supercritical carbon dioxide or gases formed in situ as a reaction product.
• a polishing pad's non-uniformity appears to be driven by the following: 1) the temperature profile of the reacting system; 2) the resulting pore expansion in areas where the temperature increases above that of the expansion temperature of the pore while the surrounding polymeric matrix remains not-so-locked in place as to be able to respond; and 3) the viscosity profile of the reacting or solidifying polymer matrix as a result of reaction and various local heating and cooling effects.
• Tg is related to the threshhold temperature for response. Polymeric microspheres above this temperature tend to grow and deform in shape.
• the microspheres' pre-casting volume and the microspheres' final volume preferably remains within 8 percent of the average pre-casting volume throughout the cast polyurethane material. Most preferably, the microspheres' final volume remains within 7 percent of the pre-casting volume throughout the cast polyurethane material.
• Literature shows a volume decrease as a function of time for pre-expanded Expancel microspheres maintained at elevated temperatures. However, the further expansion of the expanded microspheres contributes to increased non-uniformity of the polishing pads.
• Pad formulations with more unifonn density can provide more consistent removal rates and topographical control than pad formulations where this is uncontrolled, giving greater CMP process control in actual use.
• peak exotherm temperatures reach as high as 264°F (129°C). These temperatures are well above the expansion onset temperature and closely approach the temperatures of maximum expansion for Expancel microsphere 551DU40 — the unexpanded microspheres from which 551DE40d42 is produced— 275-289°F (135- 143°C).
• the density in the center of the cast cake is lower due to greater heating and the resulting greater pore expansion.
• polishing pads' porosity variation also tends to increase with increasing initial pore volume, increasing material temperatures and increasing mass of cast material. Because the pore can only expand if the surrounding polymer is still sufficiently mobile that it can rearrange with a small pressure, it is also important that the weight percent unreacted NCO of the system and the ability of the polymer backbone to order is not too low, or the pores or filler can slowly expand or segregate by density, yielding a broader density distribution.
• the polymeric material is a polyurethane.
• polyurethanes are products derived from difunctional or polyfunctional isocyanates, e.g.
• urethane production involves the preparation of an isocyanate-terminated urethane prepolymer from a polyfunctional aromatic isocyanate and a prepolymer polyol.
• prepolymer polyol includes diols, polyols, polyol-diols, copolymers thereof and mixtures thereof.
• the prepolymer polyol is selected from the group comprising polytetramethylene ether glycol [PTMEG], polypropylene ether glycol [PPG], ester-based polyols, such as ethylene or butylene adipates, copolymers thereof and mixtures thereof.
• Example polyfunctional aromatic isocyanates include 2,4-toluene diisocyanate, 2,6- toluene diisocyanate, 4,4'- diphenylmethane diisocyanate, naphthalene- 1,5- diisocyanate, tolidine diisocyanate, para- phenylene diisocyanate, xylylene diisocyanate and mixtures thereof.
• the polyfunctional aromatic isocyanate contains less than 8 weight percent aliphatic isocyanates, such as 4,4'- dicyclohexylmethane diisocyanate, isophorone diisocyanate and cyclohexanediisocyanate.
• aliphatic isocyanates are less reactive than aromatic isocyanates and release heat into the system more gradually.
• the polyfunctional aromatic isocyanate contains less than 5 weight percent aliphatic isocyanates and more preferably, less than 1 weight percent aliphatic isocyanate.
• Example prepolymer polyols include polyether polyols, such as, poly(oxytetramethylene)glycol, poly(oxypropylene)glycol and mixtures thereof, polycarbonate polyols, polyester polyols, polycaprolactone polyols and mixtures thereof.
• Example polyols can be mixed with low molecular weight polyols, including ethylene glycol, 1,2-propylene glycol, 1,3- propylene glycol, 1,2-butanediol, 1,3-butanediol, 2- methyl-1, 3- propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl- 1,5- pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol and mixtures thereof.
• low molecular weight polyols including ethylene glycol, 1,2-propylene glycol, 1,3- propylene glycol, 1,2-butanediol, 1,3-butanediol, 2- methyl-1, 3- propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl- 1,5- pen
• the prepolymer polyol is selected from the group comprising polytetramethylene ether glycol, polyester polyols, polypropylene ether glycols, polycaprolactone polyols, copolymers thereof and mixtures thereof. If the prepolymer polyol is PTMEG, copolymer thereof or a mixture thereof, then the isocyanate-terminated reaction product most preferably has a weight percent unreacted NCO range of 5.8 to 8.7.
• PTMEG family polyols are as follows: Terathane® 2900, 2000, 1800, 1400, 1000, 650 and 250 from DuPont; Polymeg® 2000, 1000, 1500, 650 from Lyondell; PolyTHF® 650, 1000, 1800, 2000 from BASF, and lower molecular weight species such as 1,2-butanediol, 1,3-butanediol, and 1,4-butanediol. If the prepolymer polyol is a PPG, copolymer thereof or a mixture thereof, then the isocyanate-terminated reaction product most preferably has a weight percent unreacted NCO range of 5 to 8.
• PPG polyols are as follows: Arcol® PPG-425, 725, 1000, 1025, 2000, 2025, 3025 and 4000 from Bayer; Noranol® 220-028, 220-094, 220-110 ⁇ , 220-260, 222-029, 222-056, 230-056 from Dow; Desmophen® 1110BD, Acclaim® Polyol 4200 both from Bayer If the prepolymer polyol is an ester, copolymer thereof or a mixture thereof, then the isocyanate-terminated reaction product most preferably has a weight percent unreacted NCO range of 4.5 to 7.
• ester polyols are as follows: Millester 1, 11, 2, 23, 132, 231, 272, 4, 5, 510, 51, 7, 8, 9, 10,16, 253, from Polyurethane Specialties Company, Inc.; Desmophen® 1700, 1800, 2000, 2001KS, 2001K 2 , 2500, 2501, 2505, 2601, PE65B from Bayer; Rucoflex S-1021-70, S-1043-46, S-1043-55 from Bayer.
• the prepolymer reaction product is reacted or cured with a curative polyol, polyamine, alcohol amine or mixture thereof.
• polyamines include diamines and other multifunctional amines.
• Example curative polyamines include aromatic diamines or polyamines, such as, 4,4'-methylene ⁇ bis-o- chloroaniline [MBCA], 4,4'-methylene-bis-(3-chloro-2,6- diethylaniline) [MCDEA]; dimethylthiotoluenediamine; trimethyleneglycol dip-aminobenzoate; polytetramethyleneoxide di-p-aminobenzoate; polytetramethyleneoxide mono-p- aminobenzoate; polypropyleneoxide di-p-aminobenzoate; polypropyleneoxide mono-p- aminobenzoate; l,2-bis(2-aminophenylthio)ethane; 4,4'-methylene-bis- aniline; diethyltoluenediamine; 5-tert-butyl-2,4- and 3-tert-butyl- 2,6- toluenediamine; 5-tert-amyl- 2,4- and 3-tert-amyl
• urethane polymers for polishing pads with a single mixing step that avoids the use of prepolymers.
• the components of the polymer used to make the polishing pad are preferably chosen so that the resulting pad morphology is stable and easily reproducible.
• MBCA 4,4'-methylene-bis-o-chloroaniline
• additives such as anti-oxidizing agents, and impurities such as water for consistent manufacturing.
• the polyurethane polymeric material is preferably formed from a prepolymer reaction product of toluene diisocyanate and polytetramethylene ether glycol with 4,4'-methylene- bis-o-chloroaniline.
• the prepolymer reaction product has a 4.55 to 8.7 weight percent unreacted NCO.
• Suitable prepolymers within this unreacted NCO range include: Airthane® prepolymers PET-70D, PHP-70D, PET-60D, PET-95A, PET- 93A, PST-95A, PPT-95A, Nersathane® prepolymers STE-95A, STE-P95, Nersathane®-C prepolymers 1050, 1160, D-5QM, D-55, D-6 manufactured by Air Products and Chemicals, Inc.
• LF600D, LF601D, LF700D, and LFG963A are low-free isocyanate prepolymers that have less than 0.1 weight percent free TDI monomer and have a more consistent prepolymer molecular weight distribution than conventional prepolymers, and so facilitate forming polishing pads with excellent polishing characteristics.
• This improved prepolymer molecular weight consistency and low free isocyanate monomer give an initially lower viscosity prepolymer that tends to gel more rapidly, facilitating viscosity control that can further improve porosity distribution and polishing pad consistency.
• the low free isocyanate monomer is preferably below 0.5 weight percent.
• the curative and prepolymer reaction product preferably has an OH or NH 2 to unreacted NCO stoichiometric ratio of 80 to 120 percent; and most preferably, it has an OH or NH 2 to unreacted NCO stoichiometric ratio of 80 to 110 percent.
• the polishing pad is a polyurethane material
• the polishing pad preferably has a density of 0.5 to 1.25 g/cm .
• polyurethane polishing pads have a density of 0.6 to 1.15 g/cm 3 . Examples The following Table provides prepolymer and microsphere formulations for casting polyurethane calces.
• formulations 1 to 9 represent formulations of the invention and formulations A to E represent comparative examples.
• comparative example A corresponds to the formulation of Example 1 of US Pat. No. 5,578,362
• comparative example B corresponds to the formulation of the IC1000TM polyurethane polishing pads sold by Rohm and Haas Electronic Materials CMP Technologies.
• the amount of unreacted NCO contained in the isocyanate-terminated prepolymers range from 5.3 to 9.11 percent.
• Adiprene® is a urethane prepolymer product of Crompton/Uniroyal Chemical.
• L325 is a H ⁇ 2 MDI/TDI - PTMEG having an unreacted NCO of 8.95 to 9.25 wt%.
• LF600D is a TDI - PTMEG having an unreacted NCO of 7.1 to 7.4 wt%.
• LF700D is a TDI - PTMEG having an unreacted NCO of 8.1 to 8.4 wt%.
• LF75 ID is a TDI - PTMEG having an unreacted NCO of 8.9 to 9.2 wt%.
• LF950A is a TDI - PTMEG having an unreacted NCO of 5.9 to 6.2 wt%.
• LFG963A is a TDI-PPG having an unreacted NCO of 5.55 to 5.85 wt%.
• LF1950A is a TDI-ester having an unreacted NCO of 5.24 to 5.54 wt%.
• Expancel® 551DE40d42 is a 30-50 ⁇ m weight average diameter hollow-polymeric microsphere manufactured by Akzo Nobel
• the microspheres represent hollow or gas-filled polymeric spheres expanded from other Expancel® microspheres. Table 2 below provides the expansion onset and expansion maximum temperatures for the microspheres before expansion.
• the polymeric pad materials were prepared by mixing various amounts of isocyanate- terminated-urethane prepolymers with 4,4'-methylene-bis-o-chloroaniline [MBCA] at the prepolymer temperatures and MBCA temperatures provided in Table 3. At these temperatures, the urethane/polyfunctional amine mixture had a gel time on the order of 4 to 12 minutes after adding of hollow elastic polymeric microspheres to the mixture.
• MBCA 4,4'-methylene-bis-o-chloroaniline
• the 551 DE40d42 microspheres had a weight average diameter of 30 to 50 ⁇ m, with a range of 5 to 200 ⁇ m; and the 551DE20d60 microspheres had a weight average diameter of 15 to 25 ⁇ m, and were blended at approximately 3,600 rpm using a high shear mixer to evenly distribute the microspheres in the mixture. The final mixture was transferred to a mold and permitted to gel for about 15 minutes.
• the mold was then placed in a curing oven and cured with a cycle as follows: thirty minutes ramped from ambient temperature to a set point of 104°C, fifteen and one half hours at 104°C (except comparative examples A-l and A-2 where this segment is changed to 5 h hours at 93°C) and two hours with a set point reduced to 21 °C.
• the molded article was then "skived" into thin sheets and macro-channels or grooves were machined into the surface at room temperature — slaving at higher temperatures may improve surface roughness.
• the formulation 8 calculation uses Uniroyal's Adiprene LFG963A S.G. of 1.15 for unfilled material
• the formulation 9 calculation uses Uniroyal's Adiprene LF1950A S.G. of 1.29 for unfilled material
• Table 4 shows a general correlation between top pad density and the predicted pad density.
• Table 5 contains the maximum exotherm temperature obtained for casting each polyurethane cake.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polyurethanes Or Polyureas (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

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